Generally, different modes of video stream data can include dummy or auxiliary frames between valid frames that disrupt previously known methods for detecting weak or invalid signals. Typically, prior art detection techniques compare a valid video frame to a current input frame to detect a weak or invalid frame. A typical prior detection apparatus will count weak or invalid frames. When this count exceeds a set threshold, a weak signal event will be generated and a receiving device can respond accordingly. However, this approach yields false positive weak signal events on data streams that include dummy or auxiliary data.
For example, some encoders can add dummy frames only and manage the time stamps for that new timing, so that the decoder detects a current dummy frame as a frame that is to be skipped and the decoder repeats the display of the old (previous) frame. In such a case, the dummy frame should be easily detected by monitoring the trick mode flag in the Packetized Elementary Stream (PES) header. However, some encoders insert a discontinuity for managing their time stamps or use a different way to encode the trick mode stream, so that the corresponding decoders will not decode the stream as desired.
Accordingly, there exists a need for a method and apparatus for detecting a weak signal in trick mode operations that overcomes the above-identified problems of the prior art.